The application claims priority to U.S. Provisional Application No. 60/444,051, which was filed on Jan. 31, 2003.
A fuel supply system includes a fuel pump assembly that pumps fuel from a fuel tank into a vehicle engine based on commands from an engine control unit. The fuel supply system also includes a fuel level sensor that measures and monitors the amount of fuel remaining in the tank. A leak detection assembly determines whether there are fuel leaks within the fuel supply system. The fuel pump assembly, fuel level sensor, and leak detection assembly each require a diagnostic function to indicate whether or not each of the respective components is operating effectively.
Traditionally, each of these fuel supply system components have either had separate control units or have been controlled by the engine control unit. When the fuel pump assembly, fuel level sensor, and leak detection assembly include separate control units, each of the control units must be connected to the engine control unit. This creates a significant number of connections to the engine control unit and requires additional wiring. This increases system cost and assembly time while potentially decreasing system reliability due to the high number of connections.
There are also disadvantages to controlling the fuel pump assembly, fuel level sensor, and leak detection assembly with the engine control unit. This configuration requires the engine control unit to have a significant amount of processing power. Further, the engine control unit must remain active when the vehicle is shut off so that the leak detection assembly can determine whether there are any fuel system leaks. Typically, it takes four to six hours to cool a fuel tank down to a temperature where leaks can accurately be detected. Requiring the engine control unit to remain active over this period of time can significantly drain power from the vehicle.
Thus, there is a need for a fuel supply and diagnostic module that operates separately from the engine control unit, but which reduces the overall number of connections to the engine control unit in addition to overcoming the other above-mentioned deficiencies in the prior art.